U.S. Pat. No. 4,196,661 discloses and claims a monitor for the knotting mechanism of a crop baler. In that patent, an upwardly springbiased slack takeup arm swings up to close a switch or raise a signal flag when the binding twine breaks or otherwise malfunctions and loses its ability to hold the takeup arm in its lowered position.
While that mechanism has proven acceptable, it is not generally capable of giving the operator a clear indication of the opposite malfunction extreme, i.e., when the twine stays tensioned when it is not supposed to, such as when the bill hook of the knotting mechanism becomes improperly wrapped with the twine and cannot be released. Moreover, the system of the '661 patent, particularly where the signal means comprises mechanical flags, is not particularly convenient for the operator, since with the use of signal flags, the operator must look over his shoulder or glance in a rearview mirror to notice that the signal flag has been operated. Furthermore, in the same respect, since the baler is provided with a number of signal flags and corresponding knotters in the '661 patent, it is necessary for the operator to perceive that one of the signal flags is behaving differently than the others, all of which move through various positions during the knotting sequence as a result of corresponding movement of their slack takeup arms.